Karl-Heinz Wrobel

The lamina propria of the bovine seminiferous tubule

SummaryThe boundary tissue of bovine testicular seminiferous tubules exhibits remarkable regional differences at the level of the seminiferous tubule proper, as compared with its terminal segment. The basal lamina of the seminiferous tubule proper is multilayered and possesses knob-like protrusions. At the level of the terminal segment the basal lamina is highly specialized; in the region of the terminal plug candelabrum-like projections of the tubular basal lamina invade the bases of the modified supporting cells up to a depth of 3.5 μm. The adjoining surface of these supporting cells is densely studded with hemidesmosomes. The elongated peritubular cells are arranged in 3–5 concentric layers around the tubulus seminiferus proper but form a loose association at the level of the terminal segment. Where the terminal segment joins the testicular straight tubule, peritubular cells may assemble to constitute a contractile spiral. Elastic tissue is situated mainly subjacent to the tubular basal lamina and to a lesser degree between the peritubular cell layers. A peritubular space lined by endothelium-like cells may surround the seminiferous tubule proper and also the transitional zone of the terminal segment.ZusammenfassungDie Membrana propria der Hodentubuli des Rindes weist im Bereich des eigentlichen Tubulus seminiferus contortus und seines Terminalsegmentes bemerkenswerte regionale Unterschiede auf. Die Basallamina des eigentlichen Tubulus seminiferus hat einen geschichteten Bau und besitzt knopfförmige Verdickungen. Im Terminalsegment zeigt die Basallamina eine zunehmende Spezialisierung; in Höhe des terminalen Pfropfes besitzt sie kandelaberartige Fortsätze, die bis zu einer Tiefe von 3,5 μm in die Basalabschnitte der hier gelegenen modifizierten Stützzellen vordringen. Die der Basallamina anliegende Oberfläche dieser Stützzellen bildet eine große Anzahl von Halbdesmosomen aus. Die flachen peritubulären Zellen umgeben mit 3–5 konzentrischen Lagen den eigentlichen Tubulus seminiferus und formieren sich im Terminalsegment zu einem stark aufgelockerten Verband. Am Übergang vom Terminalsegment zum Tubulus rectus können sich peritubuläre Zellen zu einer kontraktilen Spirale zusammenlagern. Alle peritubulären Zellen des Rindes sind dem Typ nach als Myofibroblasten einzuordnen. Elastisches Gewebe ist vor allem unter der tubulären Basallamina und in geringerer Menge auch zwischen den peritubulären Zellagen festzustellen. Um den eigentlichen Tubulus seminiferus und um die Übergangszone des Terminalsegments kann ein peritubulärer Spaltraum ausgebildet sein, der allseits von flachen endothelähnlichen Zellen begrenzt wird.

Blood Flow Regulation in the Uteroplacental Arteries

The uteroplacental arterial system is rather similar in various species (see Lundgren, 1957; Reynolds, 1963; Moll and Kunzel, 1971; Egund and Carter, 1974; Del Campo and Ginther, 1972). As shown for man and guinea pig in Figure 1, the uterine artery and the ovarian artery provide a dual arterial supply. From their anastomosis, the uterine arcade, segmental parametrial (mesometrial) off-shoots arise, divide in one or several branches and enter the uterus. These branches are short and barely accessible in the human but long and easily accessible in rodents. Inside the uterine wall the arteries form a network of arcuate (circumferential) arteries which gives rise to the coiled arteries, i.e., the radial arteries (in the strict sense) in the myometrium and the spiral arteries in the endometrium, part of which supply the placenta. There are differences in the extent to which the various components are involved in the control of uteroplacental blood flow; the basic anatomical pattern, however, is the same in the different species.

Vascular morphology of the bovine spermatic cord and testis

SummaryThe highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 μm; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.

Zur Morphologie der Ductuli efferentes des Bullen

SummaryThe ductuli efferentes of the adult bull are lined by a simple columnar epithelium with scattered small basal cells. The columnar epithelium consists of ciliated and non-ciliated cells. Among non-ciliated cells two functional stages with distinct morphological features may be identified:1.Absorptive cells possess a border of numerous, rather evenly packed microvilli with strong alkaline phosphatase activity. Between the microvilli the apical cell membrane is invaginated to form a system of narrow, coiled canaliculi which are continuous with coated vesicles and large vacuoles. Testicular fluid is reabsorbed into these vacuoles and broken down by means of lysosomal enzymes. So high levels of acid phosphatase, esterases and β-D-glucuronidase are present in the ductuli efferentes epithelium. Undigestible content of absorptive vacuoles is condensed to homogeneous, PAS-positive, protein-positive, osmiophilic, fluorescing, non membrane-bound globules.2.Non-ciliated cells with light, globules containing projections of the apical cytoplasm. These protrusions are occasionally found pinched off into the ductular lumen. We did not find any morphological evidence for phagocytosis of whole or fragmented spermatozoa by the epithelium of the bovine ductuli efferentes.ZusammenfassungDas Epithel der Ductuli efferentes des erwachsenen Bullen ist einschichtig zylindrisch mit gelegentlichen Basalzellen. Die Zylinderzellen lassen sich in Zilienzellen und Hauptzellen untergliedern. Hauptzellen treten vor allem in zwei Funktionsstadien mit unterschiedlichen morphologischen Charakteristika auf:1.Resorbierende Hauptzellen besitzen einen Saum gleichmäßig langer Mikrovilli, zwischen deren Basen sich ein System aus gewundenen Canaliculi in das apikale Cytoplasma einsenkt. Diese Canaliculi stehen mit „coated“ Vesikeln und größeren resorptiven Vakuolen in Verbindung. Innerhalb der Vakuolen findet ein Abbau von resorbierter testikulärer Flüssigkeit statt. Hieran sind lysosomale Enzyme beteiligt, wie der kräftige Ausfall der histochemischen Reaktionen auf saure Phosphatase, unspezifische Esterasen und β-D-Glucuronidase im Epithel der Ductuli belegt. Unverdaulicher Vakuoleninhalt verdichtet sich zu homogenen,PAS-positiven, eiweißhaltigen, fluoreszierenden, membranlosen, osmiophilen Globuli.2.Extrudierende Hauptzellen besitzen aufgehellte, mikrovillifreie apikale Cytoplasmaprojektionen, die mit den in ihnen gelegenen Globuli in das Ductuluslumen abgenabelt werden können. Für eine Phagocytose von ganzen oder fragmentierten Spermatozoen durch das Epithel der Ductuli efferentes des Bullen haben sich keine morphologischen Anhaltspunkte ergeben.

The fine structure of the terminal segment of the bovine seminiferous tubule

SummaryThe intratesticular excurrent duct system of the bull is composed of rete testis, tubuli recti, and the terminal segment of the seminiferous tubules. Each terminal segment is surrounded by a vascular plexus and may be subdivided into a transitional region, middle portion, and terminal plug. The modified supporting cells of the middle portion and the terminal plug no longer display the typical Sertoli-Sertoli junctions seen in the transitional region and the seminiferous tubule proper. In the region of the terminal plug a distinct central lumen is generally not observed: spermatozoa and tubular fluid must pass through an intricate system of communicating clefts between the apices of the closely attached modified supporting cells. Vacuoles in the supranuclear region of the cells in the middle portion indicate strong transepithelial fluid transport. In analogy to the epithelium of rete testis and tubuli recti, the supporting cells of the terminal segment are capable of phagocytosing spermatozoa. The vascular plexus investing the terminal segment serves a dual purpose: it is a regulatory device for fluid and sperm transport, as well as an area of increased diapedesis for white blood cells.

Intertubular topography in the bovine testis.

SummaryThe intertubular stroma of the bovine testis is composed of narrow strands between two adjacent tubules and larger tri- and quadrangular interstices between three to four tubules. The latter contain the majority of Leydig cells, larger blood vessels and testicular lymph vessels. Ley dig cells occur in groups or cords, not every cell being in close contact to a capillary, lymph vessel or venule. Between adjacent Leydig cells intercellular canaliculi and gap junctions are frequently encountered. Bovine Leydig cells are further characterized by an abundance of ribosome-associated endoplasmic reticulum, by mitochondria often containing crystalloid structures and displaying both tubular and lamelliform cristae, as well as by a relative paucity of lipid droplets and lysosomes. Independent of the size of intertubular lymph vessels their walls consist only of an endothelium of varying thickness, no typical basal lamina or associated musculature being present. The interstitial surface of the endothelium sends anchoring cytoplasmic pedicles into the subjacent ground substance and collagen fibrils. Among occasional plasma cells, mast cells and mononuclear leucocytes, a regular constituent of the intertubular region studied is a population of electron-lucid, irregularly shaped cells (light intercalated cells = LIC) with slender, pleomorphic processes. These cells are believed to be involved in testicular androgen storage and distribution.

Postnatal development of the connexion between tubulus seminiferus and tubulus rectus in the bovine testis

SummaryHistology and ultrastructure of the connexion of seminiferous and straight testicular tubules were studied in 58 bovine testes of 29 animals ranging from 4 to 52 weeks of postnatal development. In the 4th and 8th week seminiferous tubules are solid. Their non-germinal supporting cells possess spherical nuclei in a basal location and a great amount of granular endoplasmic reticulum. The straight tubules have a narrow lumen and a stratified epithelium rich in intercellular canaliculi. Between 20 and 25 weeks the seminiferous tubules acquire a lumen and develop a terminal segment, the tip of which (terminal plug) protrudes into the cup-shaped modification of the adjacent straight tubule. At 30 weeks the structural differentiation between seminiferous tubule proper and its terminal segment has proceeded: in the former spermatocytes and spermatids make their first appearance, and the supporting cells have transformed to Sertoli cells. In the latter the morphology of the supporting cell preserves a more primitive state. Starting from the 16th week and proceeding through the 30th week and further, the epithelium of the tubulus rectus close to the connexion with the seminiferous tubule becomes monolayered by rearrangement of its cells and advances along the basal lamina into the area of the seminiferous tubule. Those cells of the seminiferous tubule that are cut off from the basal lamina by invading rectus cells degenerate. Between 40 and 52 weeks the adult situation is principally achieved. The terminal segment of the seminiferous tubule is tripartite consisting of transitional region, intermediate portion, and terminal plug. The terminal segment is surrounded by a vascular plexus. The straight testicular tubule adjacent to the terminal segment is modified into a cup region encompassing the terminal plug, followed by a narrow stalk region, which is lined by simple columnar epithelium. Mononuclear free cells are a constant feature of the tubulus rectus epithelium in all stages of postnatal development.

Development of the bovine acrosome

SummaryIn the present study the development of the bovine acrosome was investigated using conventional electron-microscopical techniques as well as the phosphotungstic-acid (PTA) technique (Rambourg 1967) including enzymatic digestion experiments. As in other species and in accordance with previous light-microscopical studies (Clermont and Leblond 1955) four phases of acrosomal differentiation can be discerned: the Golgi-phase, cap-phase, acrosome-phase, and maturation-phase.In the bull no internal pattern of the acrosomal content can be observed, either with conventional uranyl acetate-lead citrate staining or with the PTA-techniques. Our results support the observation in other species (Fawcett et al. 1971) that no intrinsic polymerization or crystallization process of the acrosomal content is responsible for acrosomal shaping. Some of our results suggest the influence of external forces on acrosomal development in the bull. During the cap-phase and the acrosome-phase accumulations of smooth endoplasmic reticulum and a layer of fine filaments can be observed in the Sertoli-cell cytoplasm, immediately adjacent to the developing acrosome. A temporary influence of these structures on acrosomal development seems possible. The PTA-positive staining of the developing bovine acrosome is probably due to the presence of acrosomal glycoproteins; however, our results do not exclude the possibility that molecules other than glycoproteins contribute to the positive PTA-staining of the developing acrosome.

Spatial topography of the excurrent duct system in the bovine testis

SummaryThe rete testis of the bull is situated within an axial mediastinum and consists of approximately 30 longitudinally arranged, anastomosing rete channels. At the cranial testicular pole all rete channels empty into a common space, the area confluens reds, which is subdivided by small septa and narrow chordae retis. The area confluens always contains numerous spermatozoa and is connected with the bulbous initial portions of the efferent ductules by short, often tortuous rete tubules. Since the connection between rete and efferent ductules is situated within the tunica albuginea, the bovine excurrent duct system is not provided with an extratesticular rete as in many other mammals.Straight testicular tubules merge from all directions to connect with superficial rete channels, but the inlets are not evenly distributed. In the periphery each straight tubule begins with a cup-like structure followed by a narrow stalk region and a heavily folded portion opening either immediately into a rete channel or into a tube-like lateral rete extension.In close contiguity to the rete testis lie extremely coiled arterial portions connecting the centripetal and the centrifugal branches of the testicular artery. Since intrinsic musculature is scarcely developed in the mediastinum, and transport of rete content relies primarily on massage due to external pressure changes, the pulsatile blood flow through these coiled arteries may influence conveyance processes within the rete testis.An intimate spatial association between area confluens reds and adjacent large, thin-walled lymph vessels may facilitate a transfer of androgens into the fluid of the rete testis.

On the morphology of the brown inguinal gland of the rabbit

Die braune Inguinaldruse des Kaninchens ist eine einfach gebaute tubulose Druse. Das Epithel der Drusenschlauche ist einschichtig kubisch bis hochzylindrisch und wird von spindelformigen Myoepithelzellen unterlagert. Die Drusenzellen besitzen nahezu organellenfreie, fein granulierte Cytoplasmaprotrusionen, die weit in das Lumen hineinragen; in der Lichtung werden haufig isolierte Cytoplasmabereiche gefunden. Der Sekretionsmodus ist somit deutlich apokrin (decapitation secretion). Das endoplasmatische Retikulum ist uberall in der Zelle zu erheblich zerklufteten Cisternen erweitert; Golgi-Apparate sind sparlich. Grose, matrixreiche Mitochondrien zeichnen sich durch Armut an Cristae aus. Elektronendichte Sekretpfutzen liegen vornehmlich supranuklear; Sekretvakuolen kommen nicht vor.SummaryThe tubular brown inguinal glands of the rabbit have been studied by light and electron microscopy. The apocrine secretory cells are columnar elements with prominent apical cytoplasmic caps and protrusions extending into the glandular lumen. These protrusions contain neutral mucopolysaccharides demonstrable by light microscopy. The secretory cells are characterized by the presence of large mitochondria with scant cristae and an electron dense matrix. Electron dense plaques, presumably secretory masses, are present in the supranuclear cytoplasm. The cytoplasm contains cisternae of a granular endoplasmic reticulum. Myoepithelial cells are situated between the secretory cells and the basal lamina.ZusammenfassungDie braune Inguinaldrüse des Kaninchens ist eine einfach gebaute tubulöse Drüse. Das Epithel der Drüsenschläuche ist einschichtig kubisch bis hochzylindrisch und wird von spindelförmigen Myoepithelzellen unterlagert. Die Drüsenzellen besitzen nahezu organellenfreie, fein granulierte Cytoplasmaprotrusionen, die weit in das Lumen hineinragen; in der Lichtung werden häufig isolierte Cytoplasmabereiche gefunden. Der Sekretionsmodus ist somit deutlich apokrin (decapitation secretion).Das endoplasmatische Retikulum ist überall in der Zelle zu erheblich zerklüfteten Cisternen erweitert; Golgi-Apparate sind spärlich. Große, matrixreiche Mitochondrien zeichnen sich durch Armut an Cristae aus. Elektronendichte Sekretpfützen liegen vornehmlich supranukleär; Sekretvakuolen kommen nicht vor.